Cellulosic and lignocellulosic feedstocks and wastes, such as agricultural residues, wood, forestry wastes, sludge from paper manufacture, and municipal and industrial solid wastes, provide potentially large renewable feedstocks for the production of chemicals, plastics, fuels and feeds. Cellulosic and lignocellulosic feedstocks and wastes, composed of carbohydrate polymers comprising cellulose, hemicellulose, glucans and lignin are generally treated by a variety of chemical, mechanical and enzymatic means to release primarily hexose and pentose sugars, which can then be fermented to useful products.
Pretreatment methods are used to make the carbohydrate polymers of cellulosic and lignocellulosic materials more readily available to saccharification enzymes for such hydrolysis. Standard pretreatment methods have historically utilized primarily strong acids at high temperatures; however due to high energy costs, high equipment costs, high pretreatment catalyst recovery costs and incompatibility with saccharification enzymes, alternative methods are being developed, such as enzymatic pretreatment, or the use of acid or base at milder temperatures where decreased hydrolysis of biomass carbohydrate polymers occurs during pretreatment, requiring improved enzyme systems to saccharify both cellulose and hemicellulose.
Current practices for utilizing biomass are generally directed to providing a stream of biomass, often times from one source, and pretreating the stream of biomass by the standard methods described above. Such practices do not take advantage of integrating multiple biomass streams, such as in-process streams or waste streams, at different steps of processing and do not include economically robust treatment processes for said integrated biomass streams.
In order to achieve an economically robust process that incorporates use of integrated biomass feedstreams, a commercial process that includes hydrolysis of carbohydrates in lignocellulose from integrated biomass feedstreams is needed. To achieve the economic viability, that process must also provide high yields of sugars at high concentrations, using low amounts of chemicals, and produce a source of fermentable sugars with low toxicity toward fermentative organisms that convert sugars to value-added chemicals and fuels.
The methods described herein address ways to incorporate said integrated feedstreams into economically robust processes that meet the above needed criteria for the production of value-added chemicals and fuels.